You need something sticky that will stick the icing to the cake, honestly you don't taste it at all, but then again you won't want to buy a jar of jam just for one cake I think caramel will work, just make sure you spread it on very very very thinly (which you do with the jam as well), basically a thin scraping of caramel then scrap it off. Also only do it halfway down the sides because If you've accidentally put too much on it will ooze down the cake & out the bottom, not a good look